"This thesis is about the development of robust methods for construction of global potential energy surfaces to study the spectroscopy and dynamics of molecular systems. A potential energy surface represents the electronic energy of a molecule as a function of its geometry. This is central to how chemists view molecular systems in terms of motion across a rich energy landscape where barriers separate wells corresponding to different stable structures. The range of molecular distortions defines the potential energy surface. Computing the potential energy surface of a molecule has become a fundamental operation in modern theoretical chemistry studies. The Born-Oppenheimer approximation simplifies the Schrödinger equation (since the nuclei move slowly relative to the electrons), and enables computation of energies forming the surface. In order to develop a highly accurate surface, it is generally required to compute energies at many (typically thousands) molecular geometries. These data are then fit together using an interpolative scheme to form an analytic function. Due to interaction between states, in order to develop a surface for a particular state of interest, one often needs to include several states. In a multistate calculation, states are optimized for some choice of relative weights. It is necessary to dynamically adjust the weights, as the geometry is varied, in order to obtain a smooth and continuous surface (as using fixed weights can lead to disruptive discontinuities where states switch character). This project developed a weighting scheme based on an energy dependent functional designed to produce high accuracy and robust convergence for global surfaces. This method has been successfully demonstrated on ozone. The theoretical calculations are in good agreement with experiments, producing a significant improvement of the rate constant for the O + O₂ exchange reaction"--Abstract, page iii.
Wang, Jee C.
Chemical and Biochemical Engineering
M.S. in Chemical Engineering
Missouri University of Science and Technology
vii, 58 pages
© 2013 Phalgun Lolur, All rights reserved.
Thesis - Open Access
Potential energy surfaces -- Design and construction
Potential energy surfaces -- Mathematical models
Potential energy surfaces -- Computer simulation
Potential energy surfaces -- Analysis
Ozone -- Mathematical models
Ozone -- Computer simulation
Electronic OCLC #
Lolur, Phalgun, "Robust methods for construction of global potential energy surfaces" (2013). Masters Theses. 5372.